Method and apparatus for pattern detection

Abstract

The inventive pattern detection method and apparatus produce, from an optical image of a pattern in attention and an optical image of a pattern which should be identical to the pattern in attention, an optical image by merging the images, with a relative phase shift being imposed, and pattern information is detected or observed in the merged optical image or a signal produced from the optical image through the conversion with an opto-electric transducer means.

We claim: 
     
       1. A pattern detection method for detecting or observing a repetitive pattern on an object, said method comprising illuminating the object with coherent or partially coherent light; detecting reflected or transmitted light from the object to produce a detected optical image; splitting the detected optical image provide first and second optical images; merging the first and second optical while shifting the relative phase of said first and second optical images by 180° to produce a combined optical image; and detecting or observing pattern information in said combined optical image. 
     
     
       2. A pattern detection method according to claim 1, wherein said pattern information is information indicative of a defect in one of said first and said second patterns. 
     
     
       3. For use with a pattern which is repetitive in x and y directions, a pattern detection method comprising the steps of: splitting an optical image of the pattern in the x direction into a first plurality of optical images;   merging said first plurality of optical images, while shifting the relative phase of the first plurality of optical images by an amount dependent upon the repetitiveness in the x direction of the repetitive pattern, to produce a first merged optical image;   detecting the first merged optical image with a first opto-electric transducer to produce a first electrical signal indicative of the first merged optical image;   splitting an optical image of the pattern in the y direction into a second plurality of optical images;   merging said second plurality of optical images while shifting the relative phase of the second plurality of optical images by an amount dependent on the repetitiveness in the y direction of the repetitive pattern to produce a second merged optical image;   detecting the second merged optical image with a second opto-electric transducer to produce a second electrical signal indicative of the second merged optical image; and   detecting pattern information based on the first and second electrical signals.   
     
     
       4. A pattern detection apparatus for detecting repetitive pattern on an object, said apparatus comprising an illumination optical system for illuminating the object with a coherent or partially coherent light; a detection optical system for detecting reflected or transmitted light from the object to produce a detected optical image; an optical splitting system for splitting the detected optical image into first and second optical images; a merging optical system for merging said first and second optical images, while shifting the relative phase of said first and second optical images by 180°; and means for detecting or observing pattern information in the merged optical image. 
     
     
       5. A pattern detection apparatus according to claim 4, wherein said merging optical system includes a zoom relay lens, an adjustable multi-refraction device, half mirror, lens, diffraction grating, or Fresnel zone plate. 
     
     
       6. A pattern detection apparatus according to claim 4, wherein said illumination optical system includes means for reducing the plane wave or the displacement from the plane wave to a value smaller than the wavelength on the pattern. 
     
     
       7. A pattern detection apparatus for detecting a repetitive pattern in an object, said apparatus comprising an illumination light source for illuminating the object with a coherent or partially coherent light; a first detection optical system for detecting reflected or transmitted light in a first optical path from the object to produce a first detected optical image; a second detection optical system for detecting reflected or transmitted light in a second optical path from the object to produce a second detected optical image; a merging optical system for merging the first and second optical images while shifting the relative phase between said first and second optical images by 180° to provide a merged optical image; and means for detecting or observing pattern information in the merged optical image.